This proposal requests GCRC support to obtain pilot data on the effects of chronic and alcohol consumption on benzodiazepine receptor (BZR) distribution and density in adolescent onset alcohol dependence using [11C] flumazenil binding visualized by PET. Alterations in the GABA neurotransmitter system induced by chronic alcohol consumption represent the most likely neurochemical substrate of alcohol dependence. In two recent imaging studies, alcohol dependence in adults has been found to be associated with reduced BZR density in the cingulate cortex.